JP2004114249A - Wire breakage detector for wire saw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely detect breaking of a wire of a wire saw with a simple structure. <P>SOLUTION: In this wire saw, the wires are wound on a plurality of winding rollers in multiple rows to form wire rows, and a work is pressed on the wire rows to be cut into a number of wafers while supplying water-soluble slurry to the wire rows. The wires are grounded, a cover to take in the wire rows is mounted along the wire rows, and an electrically conductive detection bar, to which voltage is applied, is positioned and mounted under the wire rows being electrically insulated. The breaking of the wire is detected by detecting a voltage drop caused by a contact of the wire to the detection bar due to the breaking of the wire. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wire disconnection detection device for a wire saw that uses a traveling wire as a cut saw.
[0002]
[Prior art]
A slurry containing abrasive grains is supplied to a large number of wire rows that are wound around a plurality of winding rollers and travels, and a saw function is provided to the slurry. A cutting wire saw is known, and is used for cutting an ingot such as silicon into a wafer. In this case, since the wire is a single wire in principle, if the wire is cut (disconnected), not only the cutting function is lost, but if the operation is continued as it is, the work may be damaged. For this reason, a disconnection detecting device for detecting disconnection of a wire is required.
[0003]
In this case, the above-mentioned slurry has both oil solubility and water solubility, and in the former case, since the insulation property is high, disconnection can be detected by applying a current to the wire (since no current flows to the wire, And disclosed in Japanese Utility Model Laid-Open No. 61-64951 and the like). However, in the case of the latter water-soluble slurry, since the water constitutes a good conductor in which impurities such as abrasive grains are mixed, even if the wire is broken, the slurry complements this, and still remains. The state where the current is flowing may be maintained. Therefore, disconnection cannot be detected by a method in which a current is applied to the wire.
[0004]
Therefore, Japanese Patent Application Laid-Open No. 10-34515 discloses a technique in which a voltage is applied to a wire, and a detection wire that is in contact with the wire when the wire breaks is provided insulated from the wire. According to this, when the wire breaks and comes into contact with the detection wire, a current based on the voltage applied to the wire flows through the detection wire, and therefore, by detecting this state, the break can be detected.
[0005]
[Problems to be solved by the invention]
However, according to this, the wire requires equipment for applying a voltage, and since the wire is very long, the applied voltage is also unstable, which may hinder smooth operation. In addition, since the current flowing through the detection wire when the wire is broken is temporary due to the wire breaking, if this is overlooked, the wire may not be noticed. The present invention has solved such a problem, and it is possible to detect a disconnection by applying a voltage to a detection wire (bar).
[0006]
[Means for Solving the Problems]
In view of the above problems, the present invention provides a method of forming a wire row by winding a plurality of wires around a plurality of winding rollers to form a wire row, and supplying a water-soluble slurry to the wire row. In a wire saw that cuts into a large number of wafers by pressing against a row of wires, ground the wires and attach a cover that takes in the rows of wires along the rows of wires, while detecting electrical conductors on the covers in a manner that intersects the rows of wires. Applying a voltage to this bar, it is located below the wire row and insulated and attached, and detects a wire break by detecting a voltage drop due to contact with the detection bar due to wire breakage. The present invention provides a wire disconnection detection device for a wire saw.
[0007]
According to the above-described means, when the conductor wire breaks, it touches the detection bar, so that the voltage applied to the detection bar flows from the detection bar to the grounded wire, and the voltage drops. Therefore, disconnection can be detected by monitoring this voltage. In this case, the fact that the slurry has conductivity further contributes to the voltage drop. In addition, according to this configuration, it is not necessary to apply a voltage to the wire, and it is sufficient to apply the voltage only to the detection bar, so that the electrical equipment is simple. Further, since the detection is not for the current but for the fluctuation of the voltage, the detection is more reliable. Further, since the state of the voltage drop continues, there is no oversight.
[0008]
Further, in the above, the present invention is characterized in that the winding roller is provided in two front and rear directions, and the wire row forms a substantially horizontal upper extension part and a lower extension part. Pressing against the distraction provides a means for the cover to be attached to the lower distraction. That is, since the downward extension of the wire on which the detection bar is provided is substantially in a horizontal state, the slurry that has fallen on the wire drops off early, and there is little dripping on the detection bar. Therefore, since the amount of voltage drop that occurs when the slurry is applied from the state where the slurry is not applied is small, the drop width until the voltage drop that occurs when the wire touches the detection bar is relatively large, and the detection accuracy is high. , There are few false detections.
[0009]
Further, according to the third aspect of the present invention, the cover is provided so as to substantially fill the space between the two winding rollers, and the length of the cover is long according to the means in which the detection bar is attached to the center of the cover. Thus, the amount of the slurry falling on the detection bar is further reduced, so that the voltage drop amount in the initial stage is further reduced. In addition, according to the means provided with a plurality of detection bars according to the fourth aspect, the broken wire can be reliably contacted with the detection bar (even if one is disconnected, the other is still in contact). , Undetectable situations can be prevented.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view of a main part of the wire saw, and FIG. 2 is a transverse sectional view. As is well known, the wire saw includes a front winding roller (hereinafter, referred to as a front roller) 2 forcibly driven by a servomotor or the like 1 and a rear side. A wire row 5 is formed such that one wire 4 is wound around a winding roller (hereinafter referred to as a rear roller) 3 in multiple rows and travels in one direction. A groove for preventing derailment of the wire 4 is formed on the outer periphery of the front and rear rollers 2 and 3, and the wire 4 is fitted into the groove to maintain the interval (cut width). In the above example, the winding roller is constituted by the front roller 2 and the rear roller 3, but there may be three or more winding rollers.
[0011]
The ends of the wires 4 extending from the front and rear rollers 2 and 3 are respectively unreeled and wound by a bobbin 6, and during this time, the wires 4 are over-tensioned by a tension adjusting mechanism, that is, a slack removing mechanism (not shown). And looseness. In this case, since the wire 4 is run at a constant speed, the rotation speed of the bobbin 6 is controlled by a servomotor or the like 7 so that the peripheral speed at the winding diameter is constant regardless of the winding amount. ing. When the winding amount of one bobbin 6 is reduced, the front and rear rollers 2 and 3 are reversed to move the wire 4 in the opposite direction.
[0012]
The front and rear rollers 2 and 3 of this example have substantially the same diameter, and the wire row 5 formed by being wound around the front and rear rollers 2 and 3 has an upper extension 5a and a lower extension 5b in a substantially horizontal state. It is stretched. When the span of the front and rear rollers 2 and 3 is long, an idle roller receiving this may be provided in the upper extension 5a (not shown). The work 8 is set on a mount 9 provided above the upper extension 4a. When the work 8 is pressed against the upper extension 5a of the wire array 5 by a feed mechanism 11 driven by a motor or the like 10, the work 8 8 is cut into many pieces by the wire row 5.
[0013]
In this case, even if the work 8 is simply pressed against the wire 4, it is not cut as it is. Therefore, a slurry 12 mixed with abrasive grains or the like is supplied to the wire 4 and a cutting function is imparted to the slurry. As the slurry 12 used in the present invention, an environment-friendly water-soluble slurry 12 is used. The slurry 12 is provided with a slurry nozzle 13 above the upper extension 5 a of the wire row 5, and is ejected toward the wire 4 from the slurry nozzle 13.
[0014]
If the wire 4 is broken for any reason, not only the cutting function is lost but also the work 8 may be damaged. Therefore, it is necessary to detect this disconnection promptly as described above. Therefore, in the present invention, a cover 14 for taking in the wire row 5 and covering the wire row 5 is attached to the downward extension 5b of the wire row 5 and a detection bar 15 located below the wire row 5 is attached to the cover 14. Is mounted to detect disconnection.
[0015]
The cover 14 has a U-shaped cross section in which the upper side of the both side plates 14a is covered with an upper plate 14b. In this example, the cover 14 is provided with a length substantially filling the front and rear rollers 2, 3. (Long length). At the longitudinal end of the cover 14, a scattering prevention plate 16 for preventing the slurry 12 scattered from the front and rear rollers 2, 3 from being transmitted from the end of the upper plate 14b and entering the inside is provided upward. ing.
[0016]
At a position below the wire row 5 inside the cover 14 surrounded by the both side boards 14a and the upper board 14b, a detection bar 15 is stretched between the both side boards 14a in a direction crossing the wire row 5. The detection bar 15 is made of a conductor, and both ends thereof are supported by fixtures 17 made of an insulator fixed to both side plates 14a. Note that the detection bar 15 of this example is provided one at substantially the center of the cover 14, but may be plural. A fixed power supply is applied to the detection bar 15. In this example, a conductive line 18 is connected to the detection bar 15, and the voltage of the power supply 19 is applied to the conductive line 18. The power supply 19 may be a DC power supply or an AC power supply. Then, a voltage detector 20 is connected to the conductive line 18 to monitor the fluctuation of the voltage applied to the detection bar 15.
[0017]
FIG. 3 is a graph showing the fluctuation of the voltage applied to the detection bar 15 in the above configuration. When the slurry 12 is not supplied (dry state), the resistance of the circuit of the detection bar 15 becomes infinite. voltage is maintained at the initial voltage V _1. However, when the slurry 12 is supplied, the slurry 12 tries to directly descend on the detection bar 15, but this is blocked by the upper plate 14 b of the cover 14. However, the slurry 12 applied to the wire 4, since somewhat as it passes over the detection bar 15 sometimes dripping detection bar 15, the voltage drops to the operating voltage V ₂ which in the resistance value drops. Furthermore, the wire 4 is a conductor is in contact with the detection bar 15 broken, the resistance value is further lowered to decrease the detected voltage V _3.
[0018]
In order to make this possible, a grounded rotary connector or the like 21 is attached to the drive shaft of the bobbin 6 or the like, and when the broken wire 4 comes into contact with the detection bar 15, a current based on the applied voltage is transmitted from the detection bar 15 to the wire. Let it flow to 4. At this time, the use of the conductive water-soluble slurry 12 further contributes to the above-described voltage drop. Therefore, the voltage detector 20 detects this detection voltage V _3, stops the apparatus or the like is determined that disconnection would take the appropriate avoidance operation.
[0019]
In this case, in this example, since the lower extension 5b of the wire row 5 is horizontal and the length of the cover 14 is made as long as possible, the falling off of the slurry 12 applied to the wire 4 is accelerated and detected. There is little chance of dripping on the bar 15. Therefore, the voltage drop amount decreases from the initial voltages V ₁ to the operating voltage V ₂ V _d is small, a large amount of voltage drop V _s which falls on the detection voltage V ₃ from the actuation voltage V ₂ as this reaction. This means that the disconnection detection width is large, the detection accuracy is high, and the erroneous detection is reduced. When a plurality of detection bars 15 are provided, even if the broken wire 4 comes off from one of the detection bars 15, a state in which it is in contact with the other detection bars 15 can be maintained.
[0020]
【The invention's effect】
As described above, according to the present invention, a voltage is applied only to the detection bar, and a disconnection can be detected by detecting a drop in this voltage. Therefore, simple electrical equipment is sufficient, and detection can be performed for a long time. It is possible. In addition, the detection accuracy is high and the number of erroneous detections is small by contriving not to lower the resistance value of the detection bar due to falling of the slurry.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a main part of a wire saw showing an example of the present invention.
FIG. 2 is a cross-sectional view of a main part of a wire saw showing an example of the present invention.
FIG. 3 is a graph showing a voltage drop characteristic of a disconnection detecting device according to an embodiment of the present invention.
[Explanation of symbols]
2 Front Wrap Roller 3 Back Wrap Roller 4 Wire 5 Wire Row 5a 上方 Upper Extension 5b 下方 Lower Extension 8 Work 12 Slurry 14 Cover 15 Detection Bar

Claims (5)

A wire saw is formed by winding a wire in multiple rows around a plurality of winding rollers to form a wire row, and pressing a workpiece against the wire row while supplying a water-soluble slurry to the wire row to cut a large number of wafers. At the same time, the cover for taking in the wire row is attached along the wire row, while the cover is provided with a conductor detection bar in a form crossing the wire row, and a voltage is applied thereto to position the bar below the wire row. A wire disconnection detection device for a wire saw, wherein the wire disconnection is detected by detecting a voltage drop based on contact with a detection bar due to wire disconnection. Two winding rollers are provided before and after, and the wire row forms a substantially horizontal upper extension and a lower extension. The work is pressed against the upper extension, and the cover is attached to the lower extension. An apparatus for detecting wire breakage in a wire saw according to claim 1. 3. The wire disconnection detecting device for a wire saw according to claim 2, wherein the cover is provided with a length substantially filling the space between the two winding rollers, and the detection bar is attached to a central portion thereof. 3. The wire disconnection detecting device for a wire saw according to claim 1, wherein a plurality of detection bars are provided. 5. The wire breakage detecting device for a wire saw according to claim 2, wherein a center of the upwardly extending portion is supported by an idle roller, and the work is disposed on both sides thereof.

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